The present invention generally relates to excision and removal of tissue in surgical procedures, and more specifically to the use of fluid jet means for excising and removing tissue. In particular, the invention is directed toward the emulsification and removal of the lens of the eye to treat cataracts and similar disorders.
In recent years the treatment of cataracts through surgical techniques has become routine and highly successful. Generally, the affected lens of the eye is removed from its capsule within the eye, and a lens prosthesis is installed within the capsule. Through prudent choice of prosthesis and refractive power, it is often possible to provide normal vision to a patient who would otherwise be sightless.
The step of removing the cataract-beating lens was originally found to be difficult when performed by traditional surgical techniques. An incision sufficiently large to permit removal of the hard lens as a unitary object creates trauma to the delicate ocular structures, and results in prolonged recovery and patient discomfort. Moreover, it is generally considered vital to maintain the integrity of the posterior wall of the lens capsule to prevent the fibrous vitreous humour of the posterior chamber from invading the anterior chamber of the eye and affecting the iris and other important structures. The capsule is easily damaged by traditional surgical techniques.
As a result of these constraints, new techniques such as micro-cutters and acoustic emulsification have been introduced to increase the safety of the cataract removal procedure and decrease the trauma to the eye. In the former technique an inner needle reciprocates within an outer sheath that includes an intake port; vacuum pressure applied to the inner needle pulls tissue into the port, the end of the needle shears it off, and it is drawn away by the vacuum-induced flow through the needle. In this manner a hard object such as the ocular lens may be cut away incrementally and removed through a small puncture hole. In the latter technique ultrasound energy is directed toward the lens via an acoustic probe to fracture and emulsify the lens, and a vacuum channel then removes the lens detritus.
Although these techniques are generally successful, they also have limitations. Micro-cutters may fail to remove all of the lens tissue, and the instrument itself may puncture the posterior wall of the lens capsule. Likewise, the acoustic probe used in acoustic emulsification is limited in the amplitude of energy it can direct to the lens, and may fail to emulsify all of the lens tissue.